The present application relates to a semiconductor device with a trench gate structure and a method for the production thereof. The semiconductor device with the trench gate structure includes a semiconductor body with two switching electrodes. A gate electrode controls the off state and the on state between the two electrodes. The gate electrode in the trench gate structure controls a vertical switching channel through the body zone.
Such semiconductor devices are built as trench power transistors or field plate trench power transistors for voltages from approximately 10 V to more than 1000 V. The specific channel conductivity of these devices is proportional to the channel width of the switching channels. However, the greater the channel width and thus the higher the specific channel conductivity and the lower the channel resistance become, the higher will be the gate capacitance and the gate charge related thereto, which likewise increases in proportion to the channel or gate width.
In trench power transistors or field plate trench power transistors, channel resistance becomes increasingly insignificant for voltages from approximately 50 V. In order to maintain a low gate capacitance and gate charge respectively for voltages from approximately 50 V, it is useful to maintain a small switching channel width in the context of optimizing the switching characteristics of such semiconductor devices. This however affects the on capability Ron·A in conventional trench power transistors and/or field plate trench power transistors.
In conventional semiconductor devices with a trench gate structure or a field plate trench structure, the gate electrode is located in trench strips or rectangular grids or in hexagonal grids. To reduce the gate capacitance and thus the gate charge and to minimize the channel width, the cell pitch, i.e., the step width between individual trench structures, is simply increased, thus increasing the distance between the gate trenches.
The current nevertheless has to be distributed as evenly as possible over the entire width of the drift zone between the trenches, even at increased cell pitch. If however the distance between the trenches and thus the cell pitch is increased, the distance between the channel end and the centre of each individual drift zone between two trench structures is increased as well, whereby the effective drift section resistance is increased in relation to the lateral current distribution. A sheet resistance increased by the longer distance between the trench structures, however, results in a higher Ron·A. It would therefore be useful to create a semiconductor device in which the gate charge and thus the gate capacitance can be reduced without increasing the cell pitch or the distance between the trench structures respectively.
For these and other reasons there is a need for the present invention.